Where is the air ride suspension relay located?

The module is inside the truck mounted above and in front of the parking brake pedal on the firewall. The relay signal comes from the module on the dark blue with yellow trace wire into the relay but only when the system turns the compressor on. With a test light connected to a ground you should fine one relay terminal that has power full time, that is from a 50 amp fuse in the junction box. It is the power that goes through the relay to power the compressor. Many times when it loses power it is due to that fuse blowing because the compressor is failing and drawing excess current or it it staying on because of a leaking system. Connect the test light to battery positive and you should find it lights on two terminals, one is the ground for the relay and the other is through the compressor motor.
The last terminal is the power signal from the control module, but it only powers on when the system needs air. There is a service switch for the system that deactivates it so that if you jack the truck up the bags don't try to inflate and damage themselves, I have seen those fail and shut the system off, but most show a light in the dash telling you it is in service mode.